Electrode control for searchlights



Dec. 26, 1939.

w. R. FARLEY ET AL ELECTRODE CONTROL FOR SEARCHLIGHTS 2 Sheets-Sheet 1 Filed June 19, 1957 Y W. mww mam mi G B m 0 M a ITNESSES:

m William RFar/ey, Alfred A. Amer-ton Dec. 26, 1939. w. FARLEY ET AL 2,184,765

ELECTRODE CONTROL FOR SEARCH-[LIGHTS Filed June 19, 1937 I 2 Sheets-Sheet 2 43 WITNESSES: 1 #04 INVENTORS M i 42 m Wi/Zzam E. 7 0F269, Alf/662' LAT/2671072 and 0 am Ganano.

Patented Dec. 26, 1939 UNlTED STATES PATENT OFFICE I 2,184,765 v ELECTRODE ooN'rRoLron sEAncnuGn'rs vania Application June 19, 1937, Serial No. "149,164

7 19 Claims. (015176-75 Our invention relates in particular to are searchlights, such as those used for aircraft observation, where provisions are required for the automatic striking of the arc and for the autdmatic positioning of the electrodes, so as to hold the useful portion of the arc at a predetermined point with respect to the reflector of the searchlight, and the maintenance of constant current through and/or constant voltage across the are.

In the operation of arc searchlights, it is customary to strike the are by moving the energized negative electrode to make contact with the positive electrode, then drawing the negative electrode back from the positive electrode thereby drawing the arc out. This method entails a considerable time delay due to the necessity of moving the negative electrode from the position occupied when last the arc was deenergized to the engaged position before the arc can be struck. For uses, such as aircraft observation, it is necessary to strike the are very quickly. For example, in the usual system of sighting aircraft .in flight at night, the approximate location of the aircraftv is determined by a sound detector which is sensitive to the direction of the sound source and the searchlight is made to follow the movement of the sound detector or sound detector direction indicating means. When the observer.

location'of the aircraft is thus determined, the

searchlight is flashed or energized to illumlnate the aircraft so that it may be seen by an Because of the difficulty in accurately keeping the location of aircraft travelling at high speed, it is desirable that the searchlight be made to project a beam toward the aircraft as soon as possible after the location is determined. For this reason it is necessary that the searchlight are be capable of being struck very quickly. v

We have found it necessary, in the operation of arc searchlights, that the arc length and in addition, that the arc current andyor voltage, bemaintained at such predetermined values as have been found to give the maximum light outvput. It is further necessary that the useful portion of the are be maintained at a predetermined position, at or near the focus of the searchlight reflector.. Because of the rapid consumption of the electrodes in the are, it is necessary that means be provided either forcontinually feeding them to the are at a predetermined rate dependving on the rate of consumption, or that means be provided for feeding them when they have bee n consumed to such an extent as to vary the arc length, are current, are voltage orithe position of the arc with respect to the focal position of the reflector by more than a predetermined amount. v

Further while a searchlight arc is in operation, if for any reason the feeding mechanism should stop, incorrectly function, orthe electrode should be consumed to such/an extent as to become too short to be engaged by the feeding mechanism,

the arc may either beextinguished due to too great an increase in arc length, or the position of the arc may recede to a'point where the arc would be sufllciently close to the electrode holder to-allow such holder to be damaged-by heat from the are.

The feed of the positive electrode to the arc has been accomplished by a combined constant feed and supplementary thermostatically controlled feed mechanism responsive to positive electrode tip position. Such a mechanism is described in the copending application of W. H. Jacobi and I'. A. Yost, Serial No. 43,372 filed October 3, 1935, now Patent No.- 2,117,888, issued May 17, 1938 and entitled Electrode feeding mechanism for searchlights. "In such mechanisms and in system in which the positive electrode position is governed by thermostatic means alone, it has been found that, upon striking the arc after a shut-down or after recarboning, there is a tendency for the first thermostatically initiated advance of the positive electrode to be excessive. This results in a tendency in the .positioning' of the tip of the positive carbon beyond the focal'polnt or other predetermined desired position. This excessive initial advance appears to be due to the fact that the thermostat has more time lag when comparatively cool than when it has been afi'ected by heat from the are, after the arc has been burning for some time and the thermostat has become comparatively hot. One object of our invention is to provide means for obviating the hereinbefore described objectionable feature.

In past practice, the positioning of the nega tive electrode has been controlled by means responsive to either the voltage across the arc, or-

the current through the-arc. Thus, for example, in accordance with such practice, if the current through the arc should decrease below a predetermined amount, due to the negative electrode position being too distant from the positive electrode poeitlon means responsive to this decrease in current would cause the negative electrode to be advanced towards the positive electrode, until the arc current had againincreasedto the predetermined amount. .01 alternatively, in the event of the use of a control means responsive to changes in voltage across the arc, an increase in voltage across the arc would also cause the negative electrode to be advanced toward the positive electrode until the predetermined are voltage was again obtained. It has further been observed that with a given predetermined value of current through the are, or voltage across the arc, the maximum light output is obtained with a predetermined length of arc or separation between the positive and negative electrodes. It has further been observed that the positioning of the negative electrode by means responsive either to current through the arc or voltage across the arc does not necessarily result in obtaining such predetermined and optimum arc length. One object of our invention is to provide means for securing this optimum arc length as well as the predetermined value of current through or voltage across the arc to obviate the hereinbefore described objectionable feature.

An object of our invention is to provide a means whereby when an arc is deenergized for shut-down or to change electrodes, the electrodes may be made to engage and remain in the engaged position so that, when it is again desired to strike the arc, the arc may be struck quickly by merely energizing the electrodes and. moving the electrodes apart.

Another object of our invention is to provide a device which shall operate to form an are when the device is actuated and which may be operated to deenergize the arc and move the electrode into position for re-forming the arc.

A further object of our invention is to provide a means for selectively moving one electrode of an arc toward and away from the other electrode and a control system which shall cause said means to move the one electrode to engage the other electrode when the arc is deenergized and which shall cause said means to separate the electrodes to draw the are when the electrodes are energized.

Another object of our invention is to provide a device which may be actuated to move an electrode to strike an arc and which may be ,actuated to maintain the arcing tip of the electrode in a predetermined position.

Another object of our invention is to provide an electrode control mechanism for an arc searchlight which shall operate to maintain an are at a predetermined length and in a predetermined position.

A further object of our invention is to provide an arc searchlight with an electrode control system which shall have a thermostatic control and which shall operate to minimize the effect of the difference in the time lag of the thermostatic control when the arc has just been struck and the thermostat is relatively cold and after the arc has been operating long enough to cause the thermostat to be relatively hot.

Another object of our invention is to provide a control'system for the electrodes of an 'arc searchlight which shall operate to maintain a constant arc length, a constant arc current and/ or voltage and a constant arc position.

A further object of our invention is to provide a control system for the electrodes of an arc searchlight which shall operate to feed the positive electrode to the are at a continuous rate, which may be adjusted to the average rate of consumption of the electrode in the arc, and to supplement this continuous feed by a device which shall operate in response to the electrode arcing tip position to increase the rate of feed of the electrode an adjustable predetermined amount when the arcing tip has receded a predetermined amount.

Another object of our invention is to provide an arc searchlight with an electrode control system which shall operate to deenergize the electrode in the event that either electrode tip recedes a predetermined amount.

Another object of our invention is to provide an arc searchlight with a control system which shall operate to strike the arc and place the searchlight into operation, which control system shall be rendered operative only after the'ventilating means for the searchlight has been placed into operation.

These and other objects and advantages .of our invention will be readily understood by reference to the following description taken in connection with the accompanying drawings, in

which:

Figure l isa diagrammatic illustration of the operating elements and the connections thereto of the preferred embodiment of our invention; and

Figs. 2 and 3 are diagrammatic illustrations of modifications of the mechanism and circuit connections for controlling the electrode feed illustrated in Fig. 1.

In carrying out our invention we have provided a relay device which may be selectively actuated to cause one of theelectrodes of an are searchlight to move toward and away from the other electrode. This selective relay is controlled in its operation by a relay system which causes the relay device to move the one electrode to and then retract it from the other electrode to strike the arc in the event that the searchlight is energized when the electrodes are separated or in the event that the arc is broken for any reason while the searchlight remains energized. This relay system also causes the one electrode to advance to contact the other electrode when the arc is deenergized so that the electrodes will ing of the are when it is again desired to project a light beam.

Mechanism is provided to cooperate with the relay device to maintain the one electrode arcing tip in a predetermined position and the other electrode is continuously fed to the are at a rate which may be varied and which is substantially the average rate of consumption of this electrode in the arc. A mechanism is provided for keeping this other electrode arcing tip in a predeterminedposition with respect to the focal point of the searchlight reflector. Thus, the searchlight is kept in focus and a predetermined arc length is maintained. This makes for a steady continuously focused beam of unvarying' intensity.

A motor-operated ventilating fan is provided for circulating cooling air through the searchlight casing and the relay system is so connectedthe searchlight drum with the searchlight door open. This switch renders the control system inoperative to strike an are when the' door is open.

Referring to Fig. 1 of the drawings, we have shown a system for feeding theelectrodes of any reason the arc is extinguished by pulling out or any other condition not controlled by the operator, and for advancing the negative carbon to touch the positive carbon when the control means is manipulated to deenergize the arc so that the carbons will be in a position to immediately restrike the arc when desired.

Specific means for maintaining a constant voltage across the arc and a constant current flow through the arc have not been shown since such devices are well known in the art and any device suitable for this purpose may be employed.

The positive electrode H is continuously rotated by rollers 2 which are actuated by gearing mechanism from motor l3 which rotates continuously. The feeding of electrode toward the arc is accomplished by a clutch mechanism l5 which, when energized by coil IE, will establish connection between the gears l1 and I8 to actuate the feed roller l4.

Movement of negative electrode |9 toward and from the positive electrode is eifected by rollers which are actuated from gear 2| which may be selectively brought into engagement with either one of the gears 22 and 23 which are continuous- 'ly rotated by'ar motor l3. The selective movement of gear 2| is effected by solenoids 24 and 25 which, when energized, cause movement of the negative electrode from and toward the positive electrode, respectively.

Each of solenoids 24 and 25 has two operating exposed to the heat rays from the end or near,

the end of the negative electrode and which will be actuated to close its contacts when the end of the negative electrode recedes to a predetermined position. The positioning of the end of the positive electrode is likewise .governed by a thermostat 21 which is so positioned as to be aflected by the heat rays at or near the end of the positive carbon and to close its contacts in accordance with the position of the arcing tip or crater of the positive electrode. These thermostatic devices may be of any well known type of construction, but are preferably such thermostatic elements as those disclosed in the copend- 28. A fixed brush 3| is provided to supply po-'- tential to element 29 from the feed line Y. This interrupter arrangement causes intermittent energization of solenoid I6 which, in turn, causes forward movement of positive electrode II at a rate which is governed by the adjustment of brush 39. A circuit which includes the back contact 32 of thermostatic switch 21 is provided which shorts out solenoid coil l6 and, therefore,

prevents its energization except when the electrode tip is in such a position and is at such a temperature as to cause thermostatic switch 21 to open its back contact element. By this arrangement no feeding of the positive electrode is permitted until the electrode has become heated up after the initial striking of the arc.

The complete circuit for causing this feeding of the positive electrode extends from the supply conductor Y, through conductor 33, contact.

element 34, conductors 35, 36, and 31, brush 3|,

' contact strip 29, brush 30, resistance38, conductor 39, solenoid l6, conductors 40 and 4|, switch 42 and conductor 43 to the supply conductor X. The shunting circuit for the feed:-

solenoid 5 includes conductor 44, manual control switch 45, conductor 46, back contact element 32, movable contact element 41 and con- Iductor 48. By means of switch 45, this thermostatic control of th solenoid may be made operative by connecting conductors 44 and 46 or contact 50 of thermostatic switch 26, and an adjustable brush 5|, on the contactor drum 26,

which is axially movable to secure the desired time interval of energization' of the solenoid coil 49. The complete circuit for causing'this forward feed of the negative electrode extends from supply conductor Y, through conductor 33, contact element 34, conductors 35, 36 and 31, brush 3|, contact 29, brush 5|, conductor 52, coil 49, conductor 53, front contact 50, movable contact 54, of thermostatic switch 26, and conductors and 4|, switch 42 and conductor 43 to the supply conductor 'X. t

A back contact 56 is provided on the thermostat\26 for governing the energization of coil 51 of solenoid 24 to cause retraction of the negative carbon in the event that it is moved too far for ward for any reason while the arc is burning. If, for any reason, the end of the negative electrode is'operating in a position which is too far forward, movable contact 54 will engage back contact 56 to close a' circuit to energize coil 51 and thus cause a retraction of the negative carbon. This circuit extends from supply conductor Y,-through conductor 33, contact element 34, conductors 35, 36 and 31, brush 3|, contact strip 29, brush 5|, conductors 52 and 58, solenoid coil 0 51, conductor IIL bac k contact 56, movable contact 54, conductors 55 and El, switch 42 and conductor 43 to the supply conductor X. Thus it will be seen that the negative electrode arcing tip will be maintained in a position such as to cause the movable contact 54 of the thermostat 26 to be normally out of engagement with the stationary contacts 56 and 50, and as the negative electrode is consumed in the arc, contact will be made between movable contact 54 and front contact 50 to cause intermittent feed of the negative electrode towards the are by energizing solenoid coil 49.

A relay 59 is provided for governing the operation of the system to strike an are when the searchlight is first energized and the electrodes II and I9 are in contact with each other as shown in the drawings. The operation of this relay causes contact element 68 to open a circuit which comprises conductors 16 and III, contact element 68 and conductors 36 and IN, and which normally shorts out the resistance 6I when the arc is in normal operation with contact element 1 68 in closed circuit position. The opening of this circuit renders the resistance 6| effective to limit the current through the electrodes while they are in contact and while the arc is being struck. Relay 59 is provided with an operating coil 62 and a holding coil 63. The operating coil is connected through a circuit which extends from supply conductor Y, through switch 64, conductors 65 and 66, coil 62, conductors 61 and 68, contact element 69, conductors I8 and II, switch I2 and conductor I3 to supply conductor X.

The holding coil 63 of relay 59 is energized by the potential drop across resistance 6| and its current is limited by the adjustable resistance I4 which may be adjusted to cause the holding coil to release at the desired value of current in the arc circuit. This holding coil is energized through a circuit which includes resistance 6|, conductors 36, 31 and I5, coil 63, resistance I4 and conductor I6 back to the other side of resistance The energization of electrodes I9 and II is governed by contact element 34 of relay I1 and contact element I8 of relay I9. Relay TI is energized through a circuit which extends from supply conductor Y, through manual control switch 88, coil 8|, contact element 82 of relay 59, conductors 83, 92 and II, switch I2 and conductor I3 to the other supply conductor X.

The energization of relay I9 is controlled by switch 84 through a circuit extending from conductor Y, through switch 64, conductors 85 and 86, relay I9, conductor 81, contact element 88 of switch 84, conductors 89 and II, switch I2 and conductor I3 to supply conductor X. A circuit which parallels the circuit through contact element 88, which is biased to open circuit position, is provided for maintaining the energization of relay I9 and is controlled by contacts 98 actuated by relay I9. This circuit includes conductor 81, conductor 9|, contact element 88 and conductors 92 and 89.

Switch 84 also has contact element 93 which forms a circuit in parallel with contact element 69 of relay 11, which circuit includes conductors 68 and 94, contact element 93 and conductors 95 and 1|.

The movement of the negative electrode away from the positive electrode in striking the arc is under the control of the coil 96 of the solenoid 24, which is energized by the potential drop across resistance 6| due to the current flowing through the electrodes while the electrodes are in contact at the beginning of the striking of the arc and while the arc is being struck until contact'element 68 shorts out resistance 6|. The circuit for coil 96 includes resistance 6!, conductors I6 and 91, coil 96 and conductors 98 and 36 back to the other side of resistance 6|.

If, for any reason, the electrodes are'left in a A position such that they are not inv contact when 76 .the arc is shut oil and the searchlight deener- =5 gized, it is necessary that the negative carbon be moved to the positive carbon before-the arc can be struck again, and energy for actuating the motor I3 under these conditions is supplied through a circuit which extends from sup y conductor Y, through contact element 64, conductor 65, resistance 99, back contact I88 of relay II, conductors IN, 36, 31 and I82, motor I3, conductor I83, switch I04, conductors I85 and I86, contacts I8, conductor I8'I, coil I88 and conductor I89 to supply conductor X. Under these conditions the negative electrode is moved toward the positive electrode under control of coil II8 of solenoid 25 through a circuit which extends from supply conductor Y, contact element 64, conductor 65, resistance 99, contact element I88, conductors NH and 36, contact element II2, conductor H3, coil II8, conductor II4, conductors 55 and M, switch 42 and conductor 43 to supply conductor X. Coil III) is so constructed as to have fewer ampere turns than coil 96 when these coils are connected in parallel.

In order to prevent the electrodes from burning back so far as to cause the heat from the arc to damage the holding mechanism for the electrodes, a protective circuit is provided for deenergizing the arc in the event that either electrode tip recedes to a predetermined position. This circuit is under control of the thermostatic switches 26 and 21 and comprises front contacts H5 and H6 of thermostatic switches 26 and 21, respectively, which complete a circuit to short out relay coil I9 and thus cause deenergization of the are by opening contact element I8 of relay I9. This shorting circuit for coil I9 includes conductor 86 which is connected to relay I9, conductor 85, contact element H8, conductor III, front contact II5 and/or II6, contact element 54 and/or 41, conductors 55 and/or conductor 48, conductor 4I, switch 42, conductor 43, source X, conductor I3, switch I2, conductor II, conductor 92, contact element 98 and conductor 9I to the other side of the relay I9.

A fan H9 driven by motor I28 is provided for ventilating the drum of the searchlight to remove the products of combustion from the arc and to keep the searchlight from overheating. This fan motor I28 is energized by a circuit which extends from supply conductor Y, conductor I2I, motor I28, conductor I22, conductors II, switch I2, and conductor I3 to the other supply conductor X.

The control circuits for placing the are into operation are governed by the switch I2 which also controls the fan so that the fan will be in operation at all times when the arc is burning, to prevent accumulation of gas in the searchlight drum and overheating of the searchlight which might occur if the fan were separately controlled and the operator neglected to start the fan.

In order to prevent energization of the are while the door of the searchlight is open, to thus avoid injury toan operator who might be working on the mechanism inside the searchlight drum, a circuit is provided for preventing energization of the relay I9 while the door of the searchlight is open. This circuit is under control of switch 64 which is so controlled by the positioning of the searchlight door as to be closed when the searchlight door is closed and open when the door is open. It will be seen that this switch controls the energization of relay I9 through circuits which have been hereinbefore described.

- Relay 11 comprises operating coil 8| and holding coil I88. Holding coil I88 is energized by the current flowingthrough the arc, and its functigtging and purpose will be described hereina r.

In the operation of the device, the switch I2 H2 and opens its contact element 60. The next step in the operation is the closure 01' switches 45, 42 and I04. Closure of switch I04 will energize the motor I3 through a circuit hereinbefore described.

Switches 84 and 80 are closed in the order named. The closure of switch 84 energizes relay I9 which closes its contact element to establish the holding circuit hereinbefore described. When switch 80 is closed, operating coil 8I of relay TI is energized to move contact elements 69 and I00 to open circuit position and contact element 34 to closed circuit position. In this stage of the operation it will be seen that the electrodes are energized, since the main electrode energizing circuits are closed by contact element 34 of relay I1 and contact element I8 of relay I9 and power is being fed to the electrodes through resistance element 6|, since the contact element 60 of relay 59 is in the open circuit position and allows current to fiow through resistance 6I. The

' potential drop across the resistance GI and the electrodes is also effective in the motor circuit which is in parallel circuit relation with these elements and causes motor I3 to rotate. The potential drop across resistance 6| is also effective to energize coil 96 of solenoid 24 and cause gears 2I and 22 to mesh and thus retract the negative electrode I9.

At the time that relay II was energized, the circuitof the operating coil 62 of relay 59 was deenergized by the movement of contact element 69 to open circuit position. The holding coil '63 of relay 59, however, is energized by the potential drop across resistance SI and holds therelay contacts in the operated position until the negative electrode I9 is retracted sufiiciently to reduce the current to an amount which will not be suflicient to cause the drop in resistance 6| which is necessary to supply sufilcient potential to coil 63 to cause this coil to hold the contacts in operated position. The sensitivity of the holding coil may be adjusted by variable resistance I4 which is in series circuit relation with the coil 63. It will be noted that coil IIO of solenoid 25 is energized at the same time that coil 96 of solenoid 24 is energized, but since these coils are so designed and the circuit is so adjusted as to cause coil 96 to have greater strength than coil I I0 under these circuit conditions, coil 96 will effect a retraction of the electrode as hereinbefore described.

After the arc has been drawn to sufficient length to cause the holding coil of relay 59 to allow the f contacts of relay 59 to return to normal deenergized position, contact elements 60 will close the circuit shorting out resistance M. This will eliminate the potential drop across resistance 6| and solenoid coil 96 will be deenergized. Solenoid coil I I0 will be ,deenergized by the opening of contact element H2, and the operating coil 8I of relay II will be deenergized by the opening of contact element 82.

At this stage of the operation of the device the arc is burning, the movement of the negative electrode I9 is under control of solenoid coils 5! and 49 for retraction and advancing, respectively, and these coils are, in turn, controlled by the interrupter drum 28. It will be seen that so long as the negative electrode arcing tip is in a position too far advanced to cause heat rays from the electrode to actuate thermostatic switch 26, contact the retracting coil 51 of solenoid 24 will be intermittently energized through the interrupter 28 to cause intermittent retracting movements of negative electrode I9. When the negative electrode I9 is sufiiciently retracted, the heat rays from the electrode tip will be impressed upon the thermostatic switch 26 to cause separation of its contact elements 54 and 56. As the negative electrode I9 is consumed in the arc, the hottest part of the electrode recedes and so effects thermostatic switch 26 as to cause the engagement of its contact elements 50 and 54, which will cause intermittent energization of the advancing coil 49 of solenoid 25 through a circuit which includes the interrupter 28, as hereinbefore described. In this manner, the arcing tip of the negative electrode will be moved to the desired position and will be maintained in that position by the automatic feeding of the electrode toward the arc at a rate which is governed by the rate of consumption of the electrode in the arc.

The feed of the positive electrode II to the arc is governed by a similar thermostatic switch 21 and feeding of this electrode takes place only after the arcing tip of the electrode has receded to such a position as to cause the heat from the electrode crater to so effect the thermostatic switch 2'! as to cause separation of contact elements 32 and 41 which, in turn, removes the short circuit from the operating coil I6 of clutch I5 to permit intermittent feeding of the electrode at a rate which is governed by the position of brush30 on the drum of the interrupter 28.

In the event that it is desired to feed the positive electrode intermittently without relying upon the thermostatic switch control, the intermittent feed switch 45 may be opened to remove the short circuit from coil I6.

Thus both electrodes are fed to the arc to compensate for the consumption of the electrodes in the arc and the electrode tips are maintained at predetermined positions, so that the length of the arc is kept constant.

If for any reason the mechanism should fail to .move either or both of the electrodes; these electrodes might burn back to such a position as to cause damage to the electrode holders. To prevent such an occurrence, contact element II6 of H5 is so positioned as to be engaged by contact element 54 when the arc tip of negative electrode I9 has receded to a predetermined undesirable point and the' engagement of contact elements 54' and I I5 will close a circuit which will short circuit the coil relay I9.

'With the electrodes normally energized and while the arc is being maintained, the circuit to the negative electrode will be held closed by contact element 34 through the action of the current in the electrode circuit on the holding coll I08 of relay 11. It for any reason not under the control of the operator, the arc should be extinguished with the electrodes still energized, current would cease to flow through the electrodes, holding coil I08 would be deenergizedcausing contact elements 69 and I00 to close. In this position conoperating coil 62 of relay 59, extending from supply conductor X, through conductor I3. switch 12, conductors II and I0, contact element 69, conductors 68 and 51, coil 62, conductors 66 and 65 and switch 64 to supplyconductor Y. The closure of contact element I establishes a substitute circuit to the motor I3 for the motor circuit which was interrupted by the opening of contact element 34. The energization of the operating coil 62 of relay 59 also closes contact element II 2 to complete a circuit for the advancing coil IIO of solenoid 25 to cause thenegative electrode to be advanced until it engages the positive electrode. Meanwhile the closure of contact element 82 of relay 59 energizes coil 8| of relay H which opens its contact elements I00 and 69 and closes its contact element 34. This will deenergize the operating coil 62 of relay 59 but holding coil 63 of relay 59 will hold the contacts of relay 59 in the operating position, since it will now have the potential drop across it whichds caused by the heavy current flowing through resistance 0| while electrodes II and I9 are engaged.

As soon as the electrodes engage, the potential drop across resistance 6|. will act upon coil 95 of solenoid 24 which, in turn, will overcome the pull of coil III! of solenoid 25 and will cause retraction of the negative electrode to form the arc. before described in connection with the initial starting of the arc until the current in the arc has dropped to where it is no longer great enough to maintain holding coil 83 energized suiiiciently to hold the contacts of relay 59 in the energized position. Thus, it is seen that the arc will be automatically restruck if for any reason beyond the control of the operator the arc is broken.

If for any reason when it is desired to energize the Searchlight, electrodes II and I9 are not in engagement, the closure of switches I2, I04, 84 and 80 will cause the negative electrode to move into engagement with the positive electrode and to strike the are as just described in connection with the operation of re-forming the arc.

When it is desired to extinguish the arc and leave the electrodes in contact with each other, so that the arc may be struck quickly when the Searchlight is re-energized, it is only necessary to open switch I2. The opening oi. this switch will open the operating circuit of relay I9 which opens its contact element I8 to interrupt the electrode circuit. This opening of the electrode circuit will cause deenergization of the-holding coil I08 of relay 1! which will cause movement of negative electrode I9 into engagement with positive electrode II, as hereinbefore described in connection with the operation of the apparatus to restrike the arc in the event that the arc becomes extinguished. In this position of engagement of electrodes II and I9, the motor will be stalled due to being in parallel with the electrodes and resistance 6| which is very small. 11! the electrodes are left in this position, when potential is again applied to supply lines X and Y, the motor will be energized and will hold the electrodes in a position to immediately strike the are when switches 12, I04, 84 and 80, 42 and 45 are closed.

In Fig. 2,'there is shown a modification of the positive electrode control described in connection with the system of Fig. 1. The apparatus of this modification is essentially the same as that shown in- Fig. 1 and like reference characters have been applied to the corresponding parts. The thermo electrode toward the arc.

This retraction will take place as hereintact element 69 would close a circuit through the static switch 21 is provided with an auxiliary front contact 32' so positioned as to be engaged by the movable contact element 41 after it has moved a predetermined amount. With this system of control the coil I6 of the feed clutch I will be energized through interrupter 28 to cause movement of electrode II only while movable contact element 41 is moving from engagement with contact element 32 to engagement with contact element 32 while the thermostatic switch 2'! is being heated up by the heat from the tip of the positive electrode and during the movement of contact element 41 from engagement with contact element 32 to engagement with contact element 32 while thermostatic switch 21 is cooling oif after the forward movement of its movable contact has permitted movement of the positive This system has the advantage that delayin preheating of the thermostatic switch 21 and the time lag in cooling theswitch will not cause excessive feeds of the positive electrode toward the arc. The thermostatic control of the feeding of. the positive electrode to the arc may be made inoperative by the opening of switch 45, as described in connection with the operation of the system of Fig. 1. It will be noted that the spring I25 provides a resilient mounting for contact element 32' so that movable contact element 41 may continue to move, if necessary, to engagement with contact element IIB after first engaging contact element 32'.

The modification of positive electrode feed mechanism shown in Fig. 3 is designed to provide intermittent feed for the positive electrode at a rate which is substantially equal to the average rate of consumption of the electrode in the arc supplemented by an auxiliary feed under the control of a thermostatic switch to increase the rate of feed of the electrode when the arcing tip of the electrode recedes a predetermined amount. The main intermittent feed is controlled by a series circuit through the operating coil I 6 and includingthe interrupter device 28. The auxiliary feed control is governed by the contact elements I28 and I29 of thermostatic switch 21 which cooperate with a series of conducting strips I3I on the drum of interrupter 28. This auxiliary control circuit is connected in parallel with the main control circuit and gives increased total time of energization of the oper- 'ating coil I6 for each revolution of the drum 28.

The plurality of contact strips I3! are provided for the purpose of giving the coil IS a series of short energizations for each revolution rather than a long energization in order to provide inching of the electrode toward the arc and to prevent too great a feeding of the electrode toward the are, which might result from overtravel of the feeding mechanism if it were given long periods of energization. Brush I30 may be adjusted axially of the drum to vary the time interval of contact of brush I30 with contact strips IE, to thereby vary the intervals of energization of coil The protective circuit for shorting out relay I9 in the event that the arcing tip of the positive electrode recedes too far from normal position, is governed in this modification of the device by a circuit which includes conductors II! and 55, which correspond to the like-numbered conductors in the device shown in Fig. 1, movable contact 41' which is actuated by the thermostatic switch 21 and fixed contact I I6. It will be noted that contact element I28 is resiliently mounted Thus it will be seen that we have provided a mechanism for controlling the movement of the positive and negative electrodes of an arc searchlight, so that the negative electrode will be moved into contact with the positive electrode when it is desired to take the searchlight out of operation so that the electrodes will be in position for quickly striking an are when it is again desired to project a beam from the searchlight; for automatically restriking the are by properlycontrolling the movement of the negative electrode in the event that the arc pulls out or is otherwise extinguished for any cause beyond the control of the operator; for automatically striking the are when the searchlight isenergized in the event that the electrodes are not in contact when it is desired to strike an arc; for automatically feeding the positive and negative electrodes to the arc to maintain the arcing tip of the electrode at a fixed position; for securing exact adjustment of the positive electrode by a sensitive feed mechanism which will prevent over-travel of the electrode in feeding it to the arc; for rendering the mechanism inoperative to strike an arc while the door of the searchlight is open to thus prevent injury to an operator who might be working on apparatus inside the searchlight drum with the door open; and for preventing operation of the searchlight without operating the exhaust fan to thus prevent damage to the searchlight by overheating.

In compliance with the requirements of the patent statutes, we have shown and described herein the preferred embodiments of our invention. It is understood, however, that the invention is not limited to the precise construction shown and described but is capable of modification by one skilled in the art, the embodiments herein shown being merely illustrative of the.

are electrodes, an electrode feed control mechanism, supplemental electrode contact control means responsive to the deenergization of the are for causing said electrode feed control mechanism to move said electrodes into engagement, automatic arc striking means responsive to the reenergization of the electrodes for causing said electrode feed control mechanism to move said electrodes out of engagement to reestablish the arc, and position maintaining means for causing said electrode feed control mechanism to maintain a predetermined arc length.

- 2. In an arc searchlight having arcing electrodes, an electrode feeding mechanism, automatic position maintaining means causing said feeding mechanism to maintain the arcing tip of an electrode in a predetermined position, and automatic circuit control means for rendering the arc inoperative when the arcing tip of said electrode reaches a predetermined position.

3. In an arc searchlight having arcing electrodes, an electrode feeding means including an electromagnetic device, a thermostatic switch, mounting means for so positioning said switch as to cause it to be affected by the heat rays from the arcing tip of an electrode when said arcing tip recedes toa predetermined position, said thermostatic switch having normally closed contact members which are opened when the arc tip recedes to said predetermined position, circuit control means whereby the opening of said contact members causes energization of said electromagnetic device, said thermostatic switch having normally open contact members which are closed when the heat rays from the arc tip affect the thermostatic switch a predetermined amount, and auxiliary control means responsive to the closure of said normally open contact members for rendering the arc inoperative.

4. In an arc searchlight having arcing electrodes, electromagnetic means for feeding an electrode to the arc, a thermal responsive switch so positioned as to be affected by the heatrays from the arcing tip of said electrode when said arcing tip recedes to a predetermined position, said switch having normally closed contact members which are opened when the are tip recedesto said predetermined position, an energizing circuit for said electromagnetic means, circuit control means intermittently closing said circuit to said electromagnetic means for predetermined adjustable intervals of time, and auxiliary circuit means under controlof said contact members of the thermal responsive switch rendering said electromagnetic means inoperative except when- I the contact members of the thermal responsive switch are in open circuit position.

5. In an arc searchlight having arcing electrodes, electromagnetic means for feeding an electrode to the arc, circuit control means intermittently energizing said electromagnetic means, and manual means for adjusting the length of the interval of each energization of said electromagnetic means to thereby vary the rate of feed of the electrode to the arc.

6'. In an arc searchlight having arcing electrodes, electromagnetic means for feeding an electrode to said arc, circuit control means for intermittently energizing said electromagnetic means for predetermined adjustable time intervals, a thermal responsive switch responsive to the arc tip position, an auxiliary circuit means controlled by said switch for adding intervals of energization to the above-named intervals when the arc tip recedes to a predetermined position.

7. In an arc searchlight, arcing electrodes, a feeding means for each of said electrodes, automatic position maintaining means responsive to the recession-of the arcing tip of one of said electrodes a predetermined amount from a predetermined position for causing said feeding means for said one electrode to feed said electrode to the arc, and automatic auxiliary position maintaining means responsive to the position of the other electrode tip for causing said feeding means for said other electrode to move the other electrode'toward or away from the arc depending upon whether the arcing tip is displaced a predetermined amount away from or toward the are from a predetermined position.

8. In an arc searchlight, arcing electrodes, a feeding means for each of said electrodes, automatic position maintaining means responsive to the recession of the arcing tip of one of said electrodes a predetermined amount from a predetermined position for causing said feeding means for said one electrode to feed said electrode to the arc, automatic auxiliary position maintaining means responsive to the position of the other electrode tip for causing said feeding means for said other electrode to move the other electrode toward or away from the arc depending upon whether the arcing tip is displaced a predetermined amount away from or toward the are from a predetermined position, circuit control means for deenergizing the arc, and electrode contact control means responsive to the actuation of said 6 circuit control means for causing said electrode feeding means to effect engagement of the electrodes with each other preparatory to re-striking the arc.

9. In an arc Searchlight, arcing electrodes, a

10 feeding means for each of said electrodes, automatic position maintaining means responsive to the recession of the arcing tip of one of said electrodes a predetermined amount from a predetermined position for causing said feeding means 15 for said one electrode to feed said electrode to the arc, automatic auxiliary position maintaining means responsive'to the position of the other electrode tip for causing said feeding means for said other electrode to move the other electrode 20 toward or away from the arc depending upon whether the arcing tip is displaced a predetermined amount away from or toward the are from a predetermined position, circuit control means for deenergizing the arc, electrode contact control 25 means responsive to the actuation of said circuit control means for causing said electrode feeding means to effect engagement of the electrodes with each other preparatory to re-striking the arc,

supplementary circuit control means for reener- 80 gizing said are electrodes, and automatic arc striking means responsive to the reenergization of the electrodes for causing said electrode feeding mechanism to separate the electrodes and thus strike an arc.

10. In an arc Searchlight, arcing electrodes, a feeding mechanism for each of said electrodes, automatic position maintaining means responsive to the recession of the arcing tip of one of said electrodes a predetermined amount from a pre- 40 determined position for causing said feeding mechanism for said one electrode to feed said electrode to the arc, automatic auxiliary position maintaining means responsive to the position of the other electrode tip for causing said feedin rmechanism for said other electrode to move the,

other electrode toward or away from the are depending upon whether the arcing tip is displaced a predetermined amount away from or toward the arc from a predetermined position, and cir- 50 cuit control means responsive to the recession of either of the arcing tips from its normal position a predetermined amount for deenergizing the arc.

11. In combination with an arc searchlight having arcing electrodes, automatic current con- 55 trol means for maintaining a constant predetermined current fiow through the arc, electrode feeding means, and electrode position control means causing said electrode feeding means, to maintain a predetermined arc length.

12. In a light producing arcing device having an arcing electrode and a feeding mechanism for the electrode, an electrode positioning control system for causing the electrode feeding mechanism to maintain the electrode at a predeter- 65 mined position comprising, an electrode feed control means for causing said feeding mechanism to operate, a thermal responsive switch having fixed front and back contact elements and a movable contact element normally biased in contact 70 with one of said fixed contact elements and movable from contact with said one fixed contact element to contact with the other contact element when the thermal responsive switch responds a predetermined amount, auxiliary means for caus- 7 ing the heat from the arcing heat zone to afiect said thermal responsive switch when the electrode arcingtip recedes a predetermined amount, and automatic circuit control means whereby said electrode feed control means is rendered ineffective by the disengagement of said movable contact element with both of said fixed contact elements.

13. In an arc Searchlight, a ventilating mechanism for the searchlight, a mechanism for striking the Searchlight arc, and auxiliary means controlled by said ventilating mechanism for rendering said are striking mechanism inoperative while said ventilating mechanism is inoperative.

14. In a lighting device, opposing arc electrodes,

an electrode feed control mechanism for causing relative motion of the electrodes toward and away from each other, automatic electrode contact control means responsive to the deenergization of the are for causing said electrode feed control mechanism to move said electrodes into engagement, automatic are striking means responsive to the reenergization of the electrodes for causing said electrode feed control mechanism to move said electrodes out of engagement to reestablish the arc, and automatic position maintaining means for causing said electrode feed control mechanism to maintain a predetermined arc length and position.

15. In a light producing device having arcing electrodes, a normal arc feed control mechanism for the electrodes, supplemental electrode contact control means for causing said are feed control mechanism to effect engagement of the electrodes when the arc is rendered inoperative, automatic are striking and reset means responsive to energization of the electrodes while they are engaged causing said feed control mechanism to strike an arc, and position maintaining means causing said feed control mechanism to maintain the arcing tip of one of the electrodes in a predetermined position.

16. In a light producing device having arcing electrodes, 9. thermostatic device, mounting means so positioning the thermostatic device as to ren der it responsive to the position of an electrode arcing tip, said thermostatic device having first contact means which are normally closed when the position of the arcing tip is such as not to affect the thermostatic device, said thermostatic device having second contact means which are normally open but are closed when the thermostatic device is affected a predetermined amount, arc feed control means responsive to said first contact means for feeding the electrode when the arcing tip recedes sufliciently to cause the thermostatic device to open said first contact means, and circuit control-means responsive to the closure of the second contact means for rendering the arc inoperative.

17. In combination with a constant current light producing device having arcing electrodes, a feed control mechanism for each of said electrodes, means responsive to the position of the arcing tip of one of the electrodes for causing its feed control mechanism to maintain the arcing tip of said one electrode in a predetermined position, and means responsive to the position of the arcing tip of the other electrode for causing its feed control mechanism to maintain its arcing tip in a predetermined position, thereby to maintain a predetermined arc length.

18. In combination with a constant current light producing device having arcing electrodes, a feed control mechanism for each of said electrodes, a first thermal switch responsive to the a,ia4,'rcs

' position of the arcing tip of one of said electrodes,

means responsive to the operation of said first thermal switch for causing the feed control mechanism associated with said one electrode to maintain its arcing tip in a predetermined position, a second thermal switch responsive to the position of the arcing tip of the other electrode, and means responsive to the operation of said second th rmal switch for causing the feed control mech- 10 anism associated with said other electrode to maintain its arcing tip in a predetermined position, whereby the arcing tips of the electrodes are maintained in a predetermined relation and a predetermined arc length is maintained.

15 19. In combination with a light producing device having arcing electrodes and a reflector, a feed control mechanism for each of said electrodes, means responsive to the position of the arcing tip of one of the electrodes for causing its feed control mechanism to maintain the arcing tip of said one electrode'in a predetermined position with respect to the reflector, and means responsive to the position of the arcing tip of the other electrode for causing its feed. control mechanism to maintain its arcing tip in a predetermined position thereby to maintain a predetermined arc length and position.

- WILLIAM R. FARLEY.

ALFRED L. A'IHERTON. O'l'IO GQNANO. 

